1 Paris: Do you mean to tell me we are carrying illicit drugs?
2 Serron: You heard the person. They're not illicit, by definition.
3 Paris: Were they legal where you bought them?
3 Serron: Well, we probably shouldn't return to Bune in a hurry.
4 Iki Piki: The local market prices for those drugs here are huge!
4 Serron: Or we could return to Bune as soon as we've sold our cargo.

Customs authorities seems mostly concerned with the flow of goods into the place where they are based, and not so concerned with picking up illicit things heading out. Which kind of makes sense: if you're smuggling something out of the country, then it's mostly the problem of the country you're trying to take it to.

This extends to people, too. I was a bit surprised on a business trip to the USA last year, when I was passing through security to depart for Australia, that nobody whatsoever bothered to look at my passport. In my previous experience, normally someone takes a look at it and at least checks the name on the boarding pass matches. But this time nobody seemed to want to even that. I asked one of the women working security, "Don't you need to see my passport?" She replied, "We don't care who's leaving the country, we only care about who's coming in."

There are exceptions to this rule though. Several African nations, for example, run very strict checks and searches for anyone trying to carry ivory out of the country. I suppose if kangaroos were as endangered as elephants[1], you wouldn't see all those kangaroo-scrotum coin purses for sale at Australian airports.

[1] Kangaroos aren't endangered at all. All four extant species are officially listed as Least Concern species by the International Union for Conservation of Nature. In fact, they are thriving, and in some cases have extended their range and populations over what existed when Europeans arrived in Australia in the 18th century. About the only place you can't find kangaroos is in heavily built up city areas.